Molding of calcium silicate having high strength and its manufacturing method

ABSTRACT

A molding of calcium silicate having high strength, which is similar to a natural timber, wherein tobermorite, C--S--H (Calcium Silicate hydrate) and quartz are mixed, and glass fiber and pulp are added, respectively, and a Ti/Qi peak ratio of which is powder X-ray diffracted is 0.1 to 1.0, and an absolute bulk density of the molding is 0.3 to 0.7 g/cc.

DESCRIPTION

1. Technical Field

The present invention relates to a molding of calcium silicate havinghigh strength useful for building materials.

2. Background Art

A molding of calcium silicate, which is obtained by hydrothermallysynthesizing calcareous material and silicic material, has been widelyused as building material having light weight, high strength, high heatresistance, incombustibility property. In recent years, such a moldingof calcium silicate has been further improved, and there have been madevarious proposals to provide the molding of calcium silicate withworking properties such as bulk specific gravity, strength, abating,cutting, polishing, screw-nail holding property, and an adhesiveproperty.

However, in the actual state, it is not easy to obtain such a moldinghaving the above-mentioned properties, and the manufacture of thebuilding material, which is similar to the natural timber, has not beenrealized yet. Conventionally, a matrix of xonotlite, which is reinforcedwith glass fiber, is typically used as the above-mentioned typematerial. However, in such a material, since an adhesive strengthbetween glass fiber and xonotlite is low, 5 to 10% by weight ofsynthetic resin is normally added thereto so as to enhance the adhesivestrength. In fact, high adhesive strength to the glass fiber wasobtained and its bending strength was satisfied. However, such amaterial was easily burned since a small amount of synthetic resinexisted in the material. Also, heat resistance and incombustibility ofsuch a material were low, and its workability was extremely low ascompared with the timber.

DISCLOSURE OF THE INVENTION

According to the present invention, an object is to provide a molding ofcalcium silicate having high strength wherein glass fiber and pulp aredispersed and strongly adhered without including compounding syntheticresin in the composition, thereby obtaining an incombustible buildingmaterial, which is similar to a natural timber.

More specifically, the present invention provides a molding of calciumsilicate having high strength wherein tobermorite C--S--H (calciumsilicate hydrate) and quartz are mixed, and 2 to 10% by weight of glassfiber and pulp are respectively contained as a reinforcing material, aTi/Qi ratio is 0.1 to 1.0 and an absolute bulk density is 0.3 to 0.7g/cc when said molding is powder X-ray diffracted wherein Ti and Qi showintensity of the X-ray diffraction of a tobermorite crystal (002) faceand that of silica crystal (101) face, respectively. Moreover, there isprovided a method for manufacturing a molding of calcium silicate havinghigh strength which is formed of calcareous material, silicic material,and fiber as raw materials wherein the calcareous material and silicicmaterial are added such that the CaO/SiO₂ molar ratio is 0.6 to 0.9;silicic material is formed of crystalline silica and amorphous silica,the weight ratio of amorphous silica/(crystalline silica+amorphoussilica), is 0.2 to 0.8 and fiber is formed of alkali proof glass fiberand pulp in an amount of 2 to 10% by weight. The method comprises thesteps of mixing calcareous material with at least a part of theamorphous silica so as to obtain a slurry at 50° C. or less; heatingsaid slurry to 80° C. or more to be gelled; uniformly mixing saidobtained gelled material with resident material including alkali proofglass fiber; dehydrating the obtained mixture under pressure of 3 to 30kgf/cm.sup. 2 whereby a molding is obtained; heating and reacting saidobtained molding in an autoclave; and setting a Ti/Qi ratio to 0.1 to1.0 when said obtained molding is powder X-ray diffracted wherein Ti andQi show intensity of the x-ray diffraction of a tobermorite crystal(002) face and that of silica crystal (101) face, respectively.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an SEM (scanning electronic microscope) photograph showing acrystal structure of a molding of calcium silicate of Example 1 of thepresent invention;

FIG. 2 is a view explaining a method for testing an abating property ofthe molding of calcium silicate according to the present invention;

FIG. 3 is an SEM (Scanning Electron Microscope) photograph showing acrystal structure of a molding of calcium silicate of Example 5 of thepresent invention;

FIG. 4 is a powder X-ray diffraction chart of the molding of calciumsilicate of Example 5;

FIGS. 5(A), 5(B) and FIGS. 6(A) and 6(B) are SEM photographs showing abroken surface of glass fiber and that of pulp when the molding ofcalcium silicate of Example 5 is bent and broken.

BEST MODE OF CARRYING OUT THE INVENTION

According to a first invention, there is provided a molding of calciumsilicate, glass fiber and pulp are dispersed and adhered to calciumsilicate in which tobermorite, C--S--H and quartz are mixed. Eachcontent of glass fiber and pulp mixed therein ranges from 2 to 10%. Ifthe contentis below 2%, sufficient strength of the material cannot beobtained. Also, even if the content exceeds 10%, the strength of thematerial is not desirably improved.

Moreover, when powder X-ray diffraction of calcium silicate constitutingthe mode is performed, a Ti/Qi ratio is 0.1 to 1.0, and an absolute bulkdensity is 0.3 to 0.7 g/cc wherein Ti and Qi show intensity of the X-raydiffraction of a tobermorite crystal (002) face and that of silicacrystal(101) face, respectively. Therefore, it is required that strengthof matrixof calcium silicate itself be high.

For obtaining material, which is similar to a natural timber, by addingreinforcing material to calcium silicate, glass fiber is favorably usedasreinforcing material. However, in order to enhance strength of thecalcium silicate base material by use of glass fiber, the followingpoints are required. That is, strength of the matrix of calcium silicateitself must be high; adhesion strength of the matrix of calcium silicateto glass fiber must be high; and strength of calcium silicate is notreduced by erosion of glass fiber serving as reinforcing material.

Inventors of the present invention made various experiments andconfirmed the following facts.

That is, in a case that the matrix of calcium silicate was formed ofC--S--H (Calcium Silicate hydrate) and quartz, the strength of thematrix was low, and the adhesion strength of the matrix of calciumsilicate to glass fiber was insufficient. As a result, glass fiber wasdrawn from the matrix in the case of bending breakage, and a desirablestrength was not able to be obtained. Moreover, in a case that most ofthe matrix was formed of tobermorite crystal, the strength of glassfiber was lowered, and the matrix and glass fiber were simultaneouslybroken in the case of bending breakage, or glass fiber was broken beforethe breakage of the matrix. Therefore, reinforcing effect of glass fiberwas not shown. In contrast, in a case that tobermorite, C--S--H, andquartz were mixed into the matrix, and glass fiber was adhered to suchthe matrix, the strength of the matrix was high, and both adhesionstrength of the matrix of calcium silicate to glass fiber and thestrength of glass fiber itself were high. Particularly, regarding thestrength of the matrix, the Ti/Qi ratio (Ti and Qi are the same as theabove) was 0.1 to 1.0, and the high strength was shown. Then, when theTi/Qi ratio was out of the range of 0.1to 1.0, the strength of the glassfiber was lowered.

Moreover, in order to improve working properties of the material such asthe cutting of the molding, abating, polishing, screw-nail holdingproperty, 2 to 10% by weight of pulp must be adhered to the matrix. Ifthevalue is below 2%, no effect is brought about, and if the value isover 10%, incombustibility is considerably lowered.

In addition, if the absolute bulk density is below 0.3, a necessaryscrew-nail holding property cannot be expected. Moreover, if theabsolute bulk density is over 0.7, it is difficult to perform nailing orcutting, abating, and the like. Therefore, the absolute bulk density isset to 0.3 to 0.7 g/cc.

According to a second invention, there is provided a method formanufacturing the molding of calcium silicate of the first invention.

First, regarding calcareous material, hydrated lime, quicklime or milkof lime may be used. Regarding silicic material, crystalline silica andamorphous silica and its weight ratio of amorphous silica/(crystallinesilica+amorphous silica) ranges from 0.2 to 0.8. If the value is out ofthe range, the molding of calcium silicate having high strength of thepresent invention cannot be obtained. Regarding crystalline silica,normalsilica powder can be used. Regarding amorphous silica,diatomaceous earth, zeolite, silica flour can be used, but diatomaceousearth is preferably used, and its grain size may be 50 μm or less. Thecompounding ratio ofcalcareous material to silicic material is set from0.6 to 0.9 at a CaO/SiO₂ molar ratio. If the value is out of this range,the product based on the object of the invention cannot be obtained.Moreover, if the value is below 0.6, generation of tobermorite becomesdifficult. If the value is over 0.9, glass fiber is eroded, so that amolding having a desired bending strength cannot be obtained. Thecompounding ratio of calcareous material to silicic material is set topreferably 0.7 to 0.85 at the CaO/SiO₂ molar ratio.

Regarding glass fiber, a chopped strand, which is obtained by cuttingalkali proof glass fiber to have a suitable length, may be used, and itscompounding ratio is 2 to 10% by weight. If the value is below 2% byweight, a desired reinforcing effect cannot be obtained. If the value isover 10% by weight, it is difficult to perform the molding process, andthe reinforcing effect is not desirably increased. Pulp is also usedtogether with glass fiber. The use of pulp improves dispersibility ofglass fiber, and largely distributes improvement of processing andworkingof the molding in addition to reinforcing effect. A normal timberpulp is used after being disaggregated in a wet manner or a dry manner.Regarding the compounding ratio of the pulp, if the ratio is below 2% byweight, thereinforcing effect cannot be obtained. And, if the ratio isover 10% by weight, incombustibility of the molding is considerablyreduced, and the reinforcing effect is little improved.

Regarding the compound of these materials, calcareous material and atleasta part of amorphous silica are mixed with water, and used asslurry. The residual amorphous silica is added later similar tocrystalline silica. Then, the adding ratio of the final amorphous silicapreferably ranges from 0.2 to 0.8 at the amorphous silica/(crystallinesilica+amorphous silica) ratio. If the value is low, the strength of thegel after being galled is weak, and the shape maintaining property isinsufficient at the time of drawing the molding from a metal moldingafter the mixed materialsare dehydrated and molded, and the handling ofthe molding becomes difficult. Moreover, if the value is high, pressurerises too much at the time of drawing the molding from the metalmolding, and this is unfavorable in view of the manufacturing of themolding. Regarding the addition of calcareous material to amorphousmaterial, the CaO/SiO₂ molar ratio is preferably 0.8 or more. If theratio is below 0.8, gelationdoes not largely advance. In this case, itis of course that all calcareousmaterial may be added thereto. However,addition of alkali proof glass fiber is unfavorable since glass fiber iseroded by free lime. Regarding awater/solid weight ratio, there is nospecial limitation, but the value preferably ranges from 3 to 10. Atsuch a water ratio, gelation sufficiently advances, and swelling of geldoes not increase too much. Theimportant point when the materials aremixed is that the mixture is performed at temperature of 50° C. or less.If the mixture is performed at temperature of over 50° C., tobermorite,which is generated by the reaction in the autoclave, is considerablydelayed, thereis a possibility that the initial product cannot beobtained. The followingreason can be considered. That is, a large amountof C--S--H, which is difficult to transfer to tobermorite, is generatedif calcareous material and amorphous silica are mixed with each other attemperature of over 50° C. It is desirable that gelation be performed at80° C. under normal pressure. Though gel time is influenced byreactivity of amorphous silica, gel time is normally 1 to 5 hours. It ispreferable thatthere be intermittent mixing during the gel time.

Then, the remaining components are added to the above-obtained gel, anduniformly mixed. In this case, the remaing components are materialswhich were not added before gelation, and always includes the alkaliproof glassfiber. Though water is further added thereto, the water/solidweight ratio is not particularly limited. For uniformly mixing fibermaterial, the above water ratio preferably ranges from 2.0 to 4.0. As amixer to be usedin this case, a diffusion type mixer such as an omnitype mixer is preferably used. Then, mixing time within 5 minutes issufficient for thiscase. Thereafter, the mixture is introduced into themetal molding, pressurized and dehydrated to be molded. Pressure to beapplied in this case is suitably 3 to 30 kg/cm². If pressure is below 3kg/cm², the shape maintaining property, which is after drawing themolding from the metal molding, is not good, and deformation isgenerated at the time of transferring. If pressure is over 30 kg/cm²,layer-shape cracks are easily generated in the molding after the moldingis pressurized and cured. A molding box can be arbitrarily used.However, a molding box having a thickness of 100 mm or less ispreferably used since the uniformity of the reaction may be lost if thethickness is too large. The water/solid weight ratio of the obtainedmolding normally ranges from 1.0 to 3.0. In this case, the bulk densityof the dried product is about 0.3 to 0.7 g/cc.

Then, the above molding is thermally reacted in the autoclave. Thereactionis normally performed at temperature of 140° to 200° C.undersaturated aqueous vapor. If the temperature is below 140° C.,generation of tobermorite is considerably delayed, and if thetemperature is over 200° C., xonotlite is partially generated.Therefore, either condition is unfavorable since the strength of theproduct is lowered.

In view of economy and stability of the quality of the product, thereaction is preferably performed at temperature of 160° to 195° C., andmore preferably 170° to 190° C. The reaction time is set to thecondition that Ti/Qi ratio is 0.1 to 1.0 as measured by powderX-ray-diffraction of the reacted molding. For example, in Examples 1 to4 of the present invention, the reaction time is 3 to 8 hours in thecase that the temperature is 180° C., 5 to 18 hours inthe case that thetemperature is 160° C., and 2 to 6 hours in the case that thetemperature is 195° C. The present invention is, of course, not limitedto the above temperature and time. After the cured molding issynthesized, the cured molding is dried, and a final product isobtained.

The following will explain Examples 1 to 4 and comparisons 1 to 3.

2.47 kg of quicklime powder was introduced into 8.65 kg of hot waterhavingtemperature of 90° C., and slacked, so that milk of lime wasobtained. The obtained milk of lime was cooled at temperature of 32° C.Thereafter, 0.67 kg of diatomaceous earth fine powder (325 meshwhole-under) was added to the cooled milk of lime, and cold waterwasadded thereto such that the water/solid weight ratio was set to 3.5,and was uniformly mixed. Thereafter, the mixture was heated in a warmbath, and gelled at temperature of 80° to 92° C. for two hours. Aftergelation, the gelled substance was cooled to 60° C. Then, 2.02 kg ofsilica powder (Toyane silica powder 250 mesh under), 0.67 kgofdiatomaceous earth powder, and 0.37 kg of alkali proof glass fiber,and 0.37 kg of pulp were added thereto, and uniformly mixed for twominutes bythe omni type mixer. The compositions of this mixture were asfollows:

CaO/SiO₂ molar ratio: 0.83

amorphous silica/(crystalline silica+amorphous silica): 0.4

alkali proof glass fiber compounding ratio: 5%

pulp compounding ratio: 5%.

The mixture was introduced into the metal mold having an inner size of610×1220 mm, and dehydrated at 12.0 kgf/cm² to obtain a molding. Thethickness of the molding drawn from the metal mold was 18 mm.The moldingwas put in the autoclave and reacted for a predetermined time attemperature of 180° C. under saturated aqueous vapor, taken out of theautoclave, and dried in an absolute dry manner at 105° C. bya dryer. Thebulk density of the dried product was 0.54 to 0.56 g/cc. However, thesize and the thickness of the product were unchanged, that is, 610×1220mm of the size and 18 mm of the thickness.

FIG. 1 shows an SEM photograph of Example 1. In the photograph, theentire surface of quartz is covered with C--S--H (Calcium Silicatehydrate) presenting white agglomeration, and it is shown thattobermorite is partially generated.

Table 1 shows the measuring result of the physical properties of theproducts obtained according to Examples 1 to 4 and comparisons 1 to 3.

In Table 1, the products shown in the comparisons are formed such thatthe Ti/Qi ratio outside the range of 0.1 to 1.0. The bending strengthshown inTable 1 was measured in accordance with JIS-A-1408. The size ofthe object to be measured was 80 mm of the width×180 mm of the length×15mm of the thickness, and the span length is set to 100 mm.Combustibility was measured in accordance with JIS-A-1321.

Regarding the abating property, an object having the size of 50 mm oflength (X), 10 mm of width (Z) and 50 mm of thickness (Y) is cut fromthe portion close to substantially the center of the product. By use ofa blade whose angle is 28°, the object whose depth of cut is 1 mm isabated at a cutting speed of 20 mm/min. In Table 1, a symbol o denotes agood abating property in which abatement is continuous, x denotes a badabating property in which abatement is discontinuous, and Δ showsanintermediate abating property.

                                      TABLE 1                                     __________________________________________________________________________                        X-ray Dif-                                                       Autoclave    fraction                                                         Constant                                                                            SEM    Ti/Qi Peak                                                                          Bulk Bending                                                                             Ratio                                           Pressure                                                                            Observing                                                                            Intensity                                                                           Density                                                                            Strength σ                                                                    Intensity                                                                          Incombus-                                                                           Abating                              Time (hr)                                                                           Result Ratio (-)                                                                           ρ (g/cc)                                                                       (kgf/cm.sup.2)                                                                      σ/ρ.sup.2                                                                tibility                                                                            Property                      __________________________________________________________________________    Embodi-                                                                            1 3     C-S-H  0.15  0.54 86    295  1st Rate                                                                            ∘                 ments        Tobermorite                  of Flame                                         Quartz can be                Retardance                                       Observed                                                              2 4     C-S-H  0.42  0.55 118   390  1st Rate                                                                            ∘                              Tobermorite                  of Flame                                         can be                       Retardance                                       Observed                                                              3 5     C-S-H  0.58  0.54 97    333  1st Rate                                                                            ∘                              Tobermorite                  of Flame                                         can be                       Retardance                                       Observed                                                              4 8     C-S-H  0.97  0.56 84    268  1st Rate                                                                            ∘                              Tobermorite                  of Flame                                         can be                       Retardance                                       Observed                                                         Compar-                                                                            5 2     C-S-H  0.08  0.56 52    116  1st Rate                                                                            x                             isons        Tobermorite                  of Flame                                         can be                       Retardance                                       Observed                                                              6 10    Most of                                                                              1.12  0.54 63    216  1st Rate                                                                            Δ                                    Matrix is                    of Flame                                         Formed of                    Retardance                                       Tobermorite                                                           7 15    Most of                                                                              1.45  0.55 46    152  1st Rate                                                                            x                                          Matrix is                    of Flame                                         Formed of                    Retardance                                       Tobermorite                                                      __________________________________________________________________________

Example 5 will be explained as follows:

The product was obtained by the same method as Example 1 excepting thatthereaction time in the autoclave was set to 5 hours 30 minutes. FIG. 3shows an SEM photograph of the matrix of the molding of calcium silicateobtained in Example 5.

It can be understood from FIG. 3 that tobermorite and C--S--H are mixedwith each other. FIG. 4 is a chart of powder X-ray diffraction of thematrix of the molding of calcium silicate obtained in Example 5. Asshown in FIG. 4, the peak of tobermorite and that of quartz are shown,and the intensity ratio of Ti/Qi was 0.64 wherein Ti=(002) surface oftobermorite (2θ=7.82°) and Qi=(101) surface of quartz (2θ=26.65°). FIGS.5(A), 5(B) and FIGS. 6(A) and 6(B) are SEMphotographs showing the brokensurfaces of glass fiber and pulp when the molding of Example 5 is bentand broken.

More specifically, FIG. 5(A) shows the state that the surface of glassfiber is covered with a base material of calcium silicate. FIG. 5(B)showsone enlarged glass fiber, which is shown in FIG. 5(A). It can beunderstoodfrom FIG. 5(B) that C--S--H and tobermorite are stronglyadhered to the surface of the glass fiber, thereby the base material andglass fiber are strongly adhered to each other. FIG. 6(A) shows the sametype of broken surface as FIG. 5(A). Specifically, FIG. 6(A) shows thestate that the surface of pulp is covered with a base material ofcalcium silicate. FIG. 6(B) shows an enlarged pulp, which is shown inFIG. 6(A). It can be understood from FIG. 6(B) that C--S--H and part oftobermorite are strongly adhered to the surface of the pulp, thereby thebase material andpulp are strongly adhered to each other.

The following will explain Examples 6 to 8 and comparisons 4 to 6.

In Examples 6 to 8 and comparisons 4 to 6, the product was obtained bythe same method as Example 4 excepting that the ratio of amorphoussilica and the adding method were changed. The results are shown inTable 2.

                                      TABLE 2                                     __________________________________________________________________________           Amorphous                                                                     Silica/                                                                       (Crystalline                                                                        Method of Adding                                                        Silica +                                                                            Amorphous Silica                                                                        Bulk Bending                                                                             Ratio                                              Amorphous                                                                           Before                                                                             After                                                                              Density                                                                            Strength σ                                                                    Strength                                           Silica)                                                                             Gelation                                                                           Gelation                                                                           ρ (g/cc)                                                                       (kgf/cm.sup.2)                                                                      σ/ρ.sup.2 (-)                                                            Note                                   __________________________________________________________________________    Embodi-                                                                            6 0.2   0.2  0    0.54 79.6  273                                         ment 7 0.6   0.2  0.4  0.55 94.4  312                                              8 0.8   0.2  0.6  0.55 81.1  268                                         Compar-                                                                            4 0.1   0.1  0    --   --    --   Shape Maintaining                      isons                                  Property in Weak After                                                        Drawing Molding,                                                              Handling of Molding                                                           cannot be Performal                         5 0.9   0.5  0.4  0.55 45.1  149  A large Number of                           6 0.9   0.2  0.7  0.54 49.4  171  Layer-shape Cracks                                                            are Formed in Product                  __________________________________________________________________________

Industrial Applicability

According to the present invention, the molding of calcium silicatehaving bulk density of 0.3 to 0.7 g/cc is light, and the strengthratio=(bending strength)/(bulk density)² is 260 or more. Also, workingprocesses such as cutting, abating, polishing can be easily performed,no dust is generated, and holding force of bisscrew is large.Furthermore, since cracks, swelling, or pores are not generated on thesurface or the inside of the product, and the molding of the presentinvention has good incombustibility, heat resistance, and stability ofsize, the molding of the present invention can be widely used in a wallmaterial, a partition material, a floor material, and a heat insulatingmaterial.

We claim:
 1. A molding of calcium silicate having high strengthcomprising calcium silicate hydrate, quartz, tobermorite and areinforcing material made of glass fiber and pulp, whereinsaid moldingcontains 2-10 wt % of said glass fiber and 2-10 wt % of said pulp, aTi/Qi ratio obtained by powder-X-ray diffraction is 0.1-1.0, wherein Tirepresents the intensity of the X-ray diffraction of a (002) face oftobermorite crystal, and Qi represents the intensity of the X-raydiffraction of a (101) face of quartz crystal, and said molding has anabsolute bulk density is 0.3-0.7 g/cc.
 2. A method of manufacturing amolding of calcium silicate containing tobermorite and quartz and havinghigh strength, from a calcareous material, a silicic material, and afiber material, as raw materials, wherein the silicic material is formedof crystalline silica and amorphous silica mixed at a weight ratio ofthe amorphous silica to the total of the crystalline silica and theamorphous silica, of 0.2-0.8, the fiber material consists ofalkali-proof glass fiber and pulp, the calcareous material and thesilicic material are added such that the CaO/SiO₂ molar ratio is0.6-0.9, and the fiber material is added such that the amount of each ofthe alkali-proof glass fiber and the pulp is 2-10 wt %, comprising thesteps of:(a) mixing all of the calcareous material, and part or all ofthe non-crystalline silica, of the raw materials, with water to form aslurry having a temperature of 50° C.; (b) making said slurry into a gelby heating said slurry at a temperature of 80° C. or higher atatmospheric pressure; (c) uniformly mixing said gel obtained in theabove step (b) with the rest of said raw material; (d) molding a mixtureobtained in the above step (c) by dehydration at a pressure of 3-30kg/cm² to form a molding; and (f) pressurizing and heating the moldingobtained in the above step (d) in an autoclave under a saturation vaporpressure, at a temperature of 140°-200° C., for 2-18 hours until theTi/Qi ratio measured by powder-X-ray-diffraction is 0.1-1.0, wherein Tirepresents an intensity of the X-ray diffraction of a (002) face oftobermorite crystal, and Qi represents an intensity of the X-raydiffraction of a (101) face of quartz crystal, respectively.